• Preheat oven to 350°F (175°C). Line 2 baking sheets with parchment paper.

Cookie Dough

• In a large bowl, whisk together the melted butter, oil, brown sugar, and granulated sugar until smooth and glossy.
• Whisk in the egg, egg yolk, and vanilla until fully combined.
• Fold in the flour, cornstarch, baking soda, and salt until just combined. Add in the mini chocolate chips and mix until just combined.
• Scoop about 1 to 2 tablespoons of dough per cookie and roll into balls. Slightly flatten the tops. You should get about 18 to 20 cookies.
• Bake for 8–10 minutes or until the edges are lightly golden but the centers still look slightly soft and underdone. Do not overbake. Slightly soft cookies help keep the sandwiches chewy and biteable after freezing.
• Let cool completely then place the cooled cookies in the freezer for 20–30 minutes before assembling. This will help make assembling easier.

Assemble

• Scoop about ⅓ to ½ cup vanilla ice cream onto the flat side of one cookie.
• Top with another cookie and gently press until the ice cream spreads close to the edges. Use a small offset spatula or your fingers to smooth the sides if needed.
• Roll the edges in mini chocolate chips if desired. Repeat with remaining cookies
• Freeze the sandwiches for at least 1 hour, or until firm. For the best texture, freeze overnight so the ice cream sets fully and the cookies soften slightly into that classic chewy ice cream sandwich texture.